This invention relates to an apparatus for supplying fuel to an internal combustion engine, and more particularly to an apparatus for supplying fuel to the engine, wherein pressurized fuel and pressurized air are mixed in a nozzle from which fuel and air mixture is injected to an air intake passage of the engine and at least one of the pressure of the pressurized air and the pressure of the pressurized fuel is controlled in response to change in the amount of suction air to preset the pressure differential between the air pressure and the fuel pressure to a required value and to achieve an optimal air-fuel ratio for engine operations.
As a conventional fuel supplying system in an internal combustion engine, for example, which is well-known in Japanese Patent Publication No. 47-4850, two opposed nozzles are arranged in an air intake cylinder, one of which is supplied with fuel having a constant pressure and the other is supplied with pressure-adjusted air, whereby the fuel and air are mixed in the air intake cylinder to control the fuel supply.
In this kind of fuel supplying system, fuel having a constant pressure is fed from a fuel pump to a fuel nozzle opening into the air intake cylinder and constant pressure of the air fed from an air pump is controlled by a valve mechanism operable responsive to engine speeds and suction vacuum or to throttle valve opening degree and suction vacuum and then the pressure-controlled air is fed to an air nozzle opening into the air intake cylinder. The fuel and air injected from the fuel and air nozzles, respectively, are mixed in the air intake cylinder and the fuel and air mixture is supplied to the engine. However, since this type of fuel supplying system mechanically controls the amount of fuel and air injected from both of the nozzles by using a valve mechanism such as a diaphragm in response to a plurality of signals corresponding to engine speeds, suction vacuum and so on, it cannot follow various operational conditions of the engine accurately and as a result, it cannot supply fuel and air mixture having a suitable air-fuel ratio responsive to the engine operations.
Moreover, the conventional fuel supplying system requires various control mechanisms in order to achieve a proper air-fuel ratio characteristic and is complicated in structure. Further, at such a low flow rate of the fuel and air mixture as under an engine idling condition, fuel is heated and a proper fuel and air mixture cannot be supplied to the engine, resulting in engine malfunction.